Machine for lapping toothed elements



June 10, 1941.. J, M, CHRISTMAN MACHINE' FOR LAPPING TooTHED ELEMENTS e sheets-sheet 1 Original Filed April 22, 1935 www-isn;

Mgmsg June 10, 1941 J. M. cHRlsTMANy 2,245,462

f MACHINE FOR LAPPING TOOTHED ELEMENTS Original Filed April 22, 1935 6 Sheets-Sheet 2 .Julie 10 1,941- J. M. cHRlsTMAN 2,245,462

MACHINE FOR LAPPING' TOOTHED ELEMENTS I y Original Filed April `22, 1935 6 Sheets-Sheet Y E' a .LACQQQ 'W3 33,43 may Qq June 10, 1941. l

J. M. CHRISTMAN MACHINE FOR LAPPING TOOTHED ELEMENTS original Filed April 22, 1935 6 Sheets-Sheet 4 gmc/Mofa June 1o, 1941. J, M, CHRSTMAN' 2,245,462

MACHiINE lFOR LAPPING TOOTHED ELEMENTS Original Filed April 22, 1935 6 Sheets-Sheet 5 June 10, 1941. "J, M. cHRlsTMAN 'MACHINE FOR LAPPING TOOTHED ELEMENTS 6 Sheets-Sheet Original Filed April 22, 1935 Vim q Q Gkrcnww s Patented .une l0, i941 MACHINE FOR LAPPING TOTHED ELEMENTS John M. Christman, Detroit, Mich., assignor to Packard Motor Car Company, Detroit, Mich., a

corporation of Michigan Application April 22, 1935, Serial No. 17,728 Renewed May 9, 1938 29 Claims.

This invention relates to apparatus for improving radially toothed machine elements such as'gears and the like 'and is more particularly concerned with the lapping or grinding of gear teeth after the formation of the teeth by the usual milling or cutting operations.

It is common practice in .the art to which this invention relates to improve the meshing of toothed gears by a lapping operation Which involves the engaging of the gears with a lap member having corresponding teeth and eecting relative reciprocation between the gear and the lap member, a suitable abrasive being supplied to the cooperating toothed surfaces. For example, an externally toothed gear and an internally toothed lap, the latter being preferably hardened and having teeth aifording therebetween recesses Within which the gear teeth may be received snugly or with a slight clearance, are

relatively aligned axially and are reciproca-ted in an axial direction, means being provided to simultaneously urge one of the cooperating members to rotate with respect to the other to apply slight circumferential pressure between the cooperating teeth. Again, lap-ping of gears is sometimes effected by rolling a gear and a toothed lap in meshing relation, relative axial reciprocation of the gear and lap during rotation thereof being additionally applied if desired. In such an arrangement the circumferential pressure between the cooperating teeth may be that resulting from the driving of the gearby the lap or vice versa.

It has been proposed heretofore to establish the amount of circumferential pressure applied between the cooperating teeth of the gear and lap by mechanical means, for instance by` a spring device for yieldingly applying torque to the cooperating gear and lap. In practice, however, such machines have not proven Wholly satisfactory, principally because of the failure of such devices to determine in advancev the extent to which the grinding operation is to be carried out. Thus it is obvious that any satisfactory apparatus for controlling the lapping of a gear must be so constructed that a definite amount of material and no more Will be removed from the faces of the gear teeth undergoing treatment; lack of uniformity in the depth of grinding produces gears Which mesh either with too little or too great clearance.

For these and other reasons it is proposed as one form of the present invention to provide a lapping machine which is manually controlled, a skilled operator applying circumferential pressure to the gear and lap by hand, the amount of pressure and the amount of material removed from the gear during the process being determined by the operators sense of touch. The necessarily delicate control of such machines is facilitated by reorganization of the arrangement and modification of the con-struction of the component parts of the machine, as hereinafter more fully described.

Machines of this character in which the circumferential pressure is controlled manually have been constructed and are no-W fairly extensively used, but the maximum speed at which these machines can be operated is relatively loW and the output correspondingly small. Thus it is found that when a certain maximum speed is exceeded, Very damaging vibrations are induced, the whole machine shaking so violently that further increase in speed of operation Would be dangerous and Would obviously interfere with the control of the pressure by the operators sense of touch.

With machines lconstructed in accordance with the instant disclosure it is found that smooth operation can be secured when th-e machine is running at a speed more than three times greater than the normal speed of previously constructed machines. For example, it has been found by actu-al comparison of a machine of the old type and a machine constructed in accordance with the present invention that when the gear is reciprocated in the old machine at the rate of 210 strokes per minute, the operation is Wholly satisfactory, this being the normal speed for which the machine is constructed. When the speed of the old machine is increased to 370 strokes per minute, the lapping operation can be carried out with a fair degree of success, but the m-achine vibrates at a dangerous amplitude, and it is quite apparent that long continued operation at this speed would seriously damage the machine. v

A machine constructed in accord-ance with the present invention, on the contrary, Was originally Idesigned to operate at 570 strokes per minute, and the speed has been increased to ri12 strokes per minute Without the development of disturbing vibrations, the operation being so smooth that it is quite apparent that further subst-antial increase in speed may be obtained without giving rise to vibrations of serious and damaging amplitude.

The invention further contemplates the provision of a machine of this character employing a fixed lap and a reciprocating gear support in which thev circumferential pressure between the gear and lap is secured by the `application of torque to the gear support rather than to the lap, whereby the entry of oil and abrasive into the mechanism for applying such pressure may be more readily avoided, the construction simplified, and manual operation rendered more convenient. It is a further feature of the invention that the replacement of worn laps and the accurate alignment of the gear and lap are facilitated.

It is obvious that machines in which the working pressure is manually applied place much reliance on the skill of the operator and that only the trained operator will be able to effect ac curate control of the lapping of gears having different degrees of irregularity and to, detect in such gears solely by his sense of touch the eiitent to which grinding has proceeded.

Thus it is a further object of the present in- Vention to eliminate the human factor in the lapping of gears and to provide a machine which is automatically operable to determine with accuracy both the pressure applied between the cooperating teeth of the gear and lap. and the eX tent to which the grinding operation is allowed to proceed or the amount of material which is to be removed from the gear being treated. 1t is a still further object to provide a gear lapping machine in which the direction of appliedV cir-- cumierential pressure is automatically reversed.

In the lapping oi gears by any of the conven tional methods, clearance is usually provided between the cooperating teeth or the gear and lap; even in the absence of such clearance there is inevitably some lost motion or backlash in the mechanism whereby pressure is applied between the opposing faces of the teeth. Thus it is es sential in a machine which is to function auton matically to apply this pressure and to periodically reverse the same that this. clearance be taken into consideration in determining the extent to which the gear and lap will be relatively rotated when the pressure is shifted, and to permit the gear and lap to partake of additional relative rotative movement.. corresponding to the amount of material that it is desired to remove. Since the clearance or blacklash necessariiy varies in different unlapped. gears, it is. obvious that the extent of relative rotation of the gear and lap from the. position which they. occupy when one side of the gear teeth have been ground to the position which they occupy wlflen the grinding of the other side has been completed will. vary on each opera-tion. It is one ot the purposes or the present invention to compensate for this variation and toV ensure that regardless of the extent of clearance present, a substantially Xe-d amount of material will be removed from each working face of the gear teeth.

Further objects and features of the invention will be apparent from the following description taken in connection with the accompanying drawings, in which Figure 1 is a side elevation ofv a lapping machine constructed in accordance with the principles of the invention;

Figure 2 is a sectionalA view taken substantially on the line 2 2. of Figure l;

Figure 3 is a section. cn the line 31u-3.' of Figure 2;

Figure 4 is a sectional view of -a dev-ice for controlling the circumferential pressure applied to the cooperating teeth of the gear and lap and taken substantially on the line 4-f8`- of Figure 5.;

Figure 5 is a partial sectional View on the line 5 5 of Figure 1;

Figure 6 is a sectional view on the line 5-6 oi Figure 5;

Figure 7 is a sectional View on the line -l of Figure 6;

Figure 8 is a plan view of the machine shown in Figure l with parts of the casing structure broken away;

Figure 9 isa front elevation, partly in section, of a portioniof the structure shown in Figure l;

Figure l0 is a fragmentary sectional view taken on the line lll-I8 of Figure 9;

Figure 11 is a vertical sectional view of a portion of thestructure shown in Figure 1;

Figure I2 is a `fragmentary View partly in section on the line l2-I2 of Figure 11;

Figure 13 is a section on the line l3-i3 of Figure. 1l;

Figure 14 is a section on the line idf-I4 of Figure ll;

Figure 15 is a sectional View on thev line lill E of Figure 11;

Figure 16 isa horizontal, sectional View of a portion of the structure sho-wn in Figure 9A and illustrating a modified arrangementthereof;

Figures 17 to 23 inclusive vare diagrammatic representations of the mode of operation of the device shown in Figure 4;,

Figure 24 is a perspective View illustrating the application of the inventiony to a battery of gear lapping machines; and

Figure 25 is a sectional iew talren substantially on the line 25-25 of Figure 14.

In order to facilitate an understanding of the invention, reference is made to the embodiment thereof shown in thev accompanying drawings and detailed descriptive language is employed. It will nevertheless be understood that no limitation ofthe invention is thereby intended and that Various changes and alterations are contemplated such as would ordinarily occur to one skilled in the art to which the invention relates.

While various features of the" invention are applicable to gear lapping machines of other types,. as hereinbefore. explained', the preferred form of the invention. as shown in Figure 1 involves. the method of lapping gears by imparting relative 'reciprocal movement to a gear and a lap. More specifically, the machine disclosed in Figure 1: is of' the type in which the lap is provided with an internal toothed portion and is retained against movement, the gear having eX- ternal teeth and lbein'g reciprocate-d in meshing relation with the lap, Thus the machine may comprise a frame including a base 39 and a head portion 3| overlying the base, the head portion being. supported' by a standard 32 rising from the base. vA shaft- 35A having at its lower end a `reduced portion*l 36. adapted. to receive a gear 31- to. be lap-pedi, the latter being secured in position-by means. of a nut 38 or in any other conventional mannen. is clamped or otherwise secured in position in a. bracket d. The bracket and clamp-ing device are hereinafter described more fully, it being sufficient to state at this point that the arrangement isi such as to facilitate the application to and' the removal from the bracket of the shaft 35 and. the' associated gear 315.

The bracket 4l) is provided. with. an upwardly directed boss 4i which may be keyed or otherwise secured asfat 4'2 against rotation on a shaft 44. A sleeve threaded on the shaft 44 is provided at its lower endv with an annular flange 48 which is arranged to be gripped between a .cooperating iiangevon a collar 49 and the upper end of the boss 4l, the collar having threaded engagement with the boss. The bracket 40 is' thus firmly secured to the shaft 44 for rotation and reciprocation therewith, but the rigidity of the connection may be increased and the possibility that play may develop as `the result of wear may be eliminated by further clamp-ing the boss 4| to the shaft 44 as shown in Figures 11 and 13. Thus a wedge member 52 seated in an aperture in the boss 4| may be drawn into binding engagement with the shaft 44 by a bolt 53 having threaded engagement with the wedge member.

As shown more particularly in Figures 2 and 3,

'the shaft 44 is supported adjacent the upper end thereof in a bearing guide 55 and is operatively iconnected by means of a pitman 58 to an eccentric 59 formed on or secured to a shaft 60, the latter being carried by the head portion of the frame and having secured thereto at its outer end a pulley 62 which may be driven by a belt 63 from a motor 65.

It will Fbe appreciated that by means of the mechanism thus far described, rotation of the shaft 50 will effect reciprocation of the shaft 44, the bracket 48, the shaft 35, and the gear 31 to be lapped, gear 31 meshing during the operation with a stationary lap 68 which may be supported; rigidly on the base 30 of the frame in the manner described more in detail hereinafter. Preferably the ecrcentricity of the member 59 is suflicient to ensure a fairly long stroke of the gear 31. For instance, while it is preferred that the gear 3l shall not be actually disengaged from the lap 68 at either end of the stroke of the gear, the length of the stroke may be greater than half the thickness of the gear as measured axially, substantial bodily displacement as distinguished from mere vibratory movement fbeing imparted to the gear so as to ensure maximum relative linear speed of the contacting toothed surfaces of the gear and lap and to promote uniformity of abrading action.

It is due in large measure to the coordination of the several parts of the mechanism by disposition thereof in the manner indicated in the drawings that the high speed of operation hereinbefore referred to is attained. Thus it is important that the means for effecting reciprocation of the gear to be lapped and of the shafts which support the same be lo'cated substantially adjacent the upper ends of these shafts, and

that the means which serves to guide the shafts during reciprocation, and which may also be employed for the purpose of applying pressure between the cooperating teeth of the gear and lap, be disposed at a lower point, and preferably fairly close to the gear and lap.

Guide means of this character, of which the principal function is to ensure proper control of the gear to enable the teeth thereof to follow the teeth of the lap, is associated with either of the shafts 35 and 44, and preferably the latter. For instance, if the gear and lap have straight teeth, it is desiralble to prevent rotation of the shafts 44 and 35 during reciprocation thereof,k

whereas if the gear and lap have twisted or helical teeth, or are of some other configuration, the shafts should be rotated accordingly'on their -own axis during reciprocation.

.the guide means comprises one or more cooperating tongue and groove elements, such elements constituting in eiect a cam device in the event the teeth of the gear and lap are not straight. Thus the shaft 44 may be provided with an enlarged portion having generally axially directed teeth l0 thereon, these teeth cooperating with corresponding internal teeth on a sleeve l5 which surrounds the shaft, an inner sleeve 'l2 of bearing metal being preferably cast within the sleeve 'I5 for this purpose, right and left-hand spiral grooves 'I3 being formed in the inner surface of the sleeve 'l5 to lock the bearing metal against displacement with respect to the sleeve. Since the invention is illustrated as applied to the lapping of a helically toothed gear, the teeth 'lll are constructed to afford a corresponding helix angle, it being understood that in the event a gear having straight teeth is being lapped, the teeth 'l0 will be correspondingly straight.

The sleeve 'I5 is supported for rotation in the head portion of the frame and it is provided at its lower end with an annular flange IE having ka toothed periphery which is engaged by a rack '18, the latter rbeing supported for reciprocation in a substantially horizontal plane. In lieu of the ralck 18, which may be reciprocated in a manner hereinafter described by mechanism operable automatically to control the abrading action, an arrangement such as that shown in Figure 16 may be employed in which the flange 16 of the sleeve 'l5 is provided with' a toothed portion arranged to cooperate with a worm `lil, the latter being secured to a shaft 88 which is rotatable manually by means of a hand wheel 82. A flexible element 84 may be provided at the lower end of the head portion of the frame to prevent the discharge of lubricant therefrom without interfering with the reciprocal and rotary movements of the shaft 44 and to seal the cooperating toothed elements l0, 'l2 and I5 against the entry of dust, lapping compound, or other foreign and afbrasive material.

In order that the shaft 44 may be permitted to rotate freely without disturbing the connection thereof to the shaft 6l), the shaft 44 may be formed above the threaded portion 'I8 thereof in two sections, for instance as shown in Figure 9, any conventional type of rotating coupling such as that indicated generally at 'll being introduced between the two sections of the shaft.

Assuming that the sleeve '15 is held against rotation, the shaft 44 will be rotated during vertical reci-procation thereof by reason of the cooperation of the teeth 'lil of the shaft with the corresponding teeth on the sleeve. When, however, the sleeve l5 is rotated by reciprocation of the rack 78 or by rotation of the hand wheel 82 and worm 1S, the sleeve will act through the teeth 'I0 to effect a slight rotation of the shaft 44 in one direction or the other. Thus the bracket 40, shaft 35, and gear 3l may be rotated to an extent sulicient to apply pressure between Thus while the mechanism provided for thisy purpose may be associated with the lap to apply torque thereto, it is preferably disposed above the base of the machine and arranged to' operate directly upon the gear being lapped in order to avoid the discharge of abrasive .and of particles of the removed material on and into the mechanism. At the same time it is desirable that this mechanism should be located at a point as close to the lap as is possible, bearing in mind the fact that the machine may be required for the lapping of gear clusters and the like having considerable length. Thus machines of this character are intended to perform delicate operations requiring very small tolerances and if circumferential pressure is supplied to the gear supporting shaft at a point considerably above the gear and lap, the torsional elasticity `of the shaft may be suiiicient to prevent accurate work. Therefore the necessary circumferential pressure is preferably applied by mechanism such as shown in Figure 9 through sleeve l5, the cooperating helical threads on the sleeve and gear supporting shaft being sufficiently close to' the gear and lap to prevent undesirable torsional springing of the shaft.

Returning to the bracket Ml, it will be observed that this bracket is generally U-shap-ed in horizontal section and is provided on each of the two flat sides thereof with vertically disposed guide strips t defining common vertical planes. At the lower end of the bracket lo is secured a plate l'l having an aperture 38 therein which is open at the front side. The plate Si is further provided with a substantially conical seat .Slo arranged to engage a corresponding seat on a member 9i, the latter being pinned or otherwise secured as at S2 to the upper end of the shaft 35. A generally rectangular member @il surrounds and partially overlies the upper end of the member Si and is received snugly within the bracket lill, being retained againsty rotation therein by engagement with the guide strips 85. A plurality of friction plates et, of which alternate plates are keyed to the members 94 and 9|, are interposed between these members and function as a frictional coupling therebetween to normally prevent relative rotation thereof. Seated on the upper face of the member 94 is a plate 9'! having a hardened insert S8 in the central portion thereof against which pressure may be applied to increase the frictional contact of the interleaved plates S5.

The principal purpose of this arrangement is to facilitate indexing of the gear, it being advisable to register the teeth of the gear with different lap teeth so that greater uniformity of tooth contour may be secured by, averaging the defects of the teeth of the lap and gear. Thus with the present construction this may be readily accomplished by releasing the pressure applied to the plate Si! in the manner hereinafter described and raising the shaft 35 manually to withdraw the gear 3l from engagement with the lap. When thus withdrawn the gear may be rotated to a new position and replaced in meshing relation with the lap, the friction connection between the bracket ifi and the shaft 35 permitting the firm retention of the latter in any position of rotative adjustment with respect to the bracket Ml.

Adjacent the upper end of the bracket Lili, extending frorn one side wall of the bracket to the other and journalled therein, is a spindle provided with a handle |i!| whereby the same may be rotated. The spindle ld!! is provided with an eccentric portion let on which is journalled an arm loll depending from the shaft and carrying at its lower end an adjustable abutment H25 which is adapted to engage the plate 91 and to apply pressure thereto when the handle loi is rotated in one direction and which may be withdrawn from the plate by rotation of the handle in the other direction. ln order that the arm |94 may be readily withdrawn from the plate Sl to facilitate the withdrawal of the shaft 35 from the bracket lil for the replacement of gears 3l and to permit release of the shaft for indexing, a spring itt is provided, this spring being secured at one end to the arm |04 and at the other end to a sleeve lill which is secured to the eccentric portion of the shaft |60. rlhis spring is under suiiicient tension to swing the arm HM forwardly and upwardly as soon as vpressure between this arm and the plate Si is released. In order that the arm it may be readily returned to its operative position, that portion of the arm which surrotmds the spincile |98 is provided with an annular recess |09 and an abutment lli! secured to the spindle |60 is arranged to ride in this recess, the arrangement being such that as the handle le! is rotated toward the position in which pressure is exerted downwardly on the arm It, the arm |84 is swung toward its operative position by engagement of the abutment die with the arm |04 at one end of the recess IEBS.

While the lap 68 may be secured in position in any conventional manner, the arrangement shown in Figures 11 and 12 is preferred. This arrangement includes a catch basin H2 which is supported in the base E@ of the frame, and an annular element ||3 resting on the upper flange H4 of the catch basin. The element ||3 is provided with an annular recess affording a substantially horizontal surface H6 and a generally cylindrical surface H1, these surfaces being accurately machined and centered with respect to the axis of the shaft 35. Corresponding accurately finished surfaces are provided on the lap 68 which seats therein, an annular passage ||9 communicating with downwardly directed discharge passages |276) being formed in the member ||3 so that abrasive, oil, dirt, and the like may be readily removed from the surfaces ||6 and ||1 with which the lap engages. A bell-crank H2', pivotally supported on the base 30, is provided for use in raising and lowering the catch basin i2.

The upper surface of the lap is engaged by a kplurality of clamp elements |2|, each of which is seated at its outer end on the element ||3, and at its inner end with the lap t8, and is provided intermediate its ends with an aperture |22 through which a bolt |24 may extend, the bolts being threaded in the element i I3. The lap may be thus placed in accurate alignment with the gear undergoing treatment and is frictionally clamped on the base 30 of the frame against Unintentional displacement. v

The catch basin ||2 may be filled or nearly filled with an abrasive mixture, for instance emery in suspension in oil, and thus on each downward stroke of the gear 3'! a small quantity of the abrasive is supplied to the toothed portion of the gear. In order that the emery may not settle but will remain in generally uniform suspension, a pipe |15 may be fitted into the lower end of the catch basin and compressed air discharged through this pipe into the mixture so that the latter is maintained in a state'of agitation. The compressed air may be derived from any source; for instance by a small pump driven from the burnishing machine.

The machine thus far described is so constructed as to provide either for manual or automatic control of the working pressure applied to the working faces of the gear and lap and as the result of the simplicity of the construction, extremely high speeds of operation are possible without the development of annoying or serious vibration. It is important to note that reciprocation of the gear is effected by a simple nonadjustable crank and pitman drive imparting a fixed reciprocal stroke to the gear supporting shaft. The use of cumbersome mechanism for displacing or altering the length of the stroke is avoided, it havingbeen found that the inclusion of mechanism of this character contributes largely to the development of the harmful vibrations hereinbefore referred to. When applied to the lapping of gears having helical teeth, the necessary rotation of the gear supporting shaft lduring reciprocation thereof and the application of torque for applying the working pressure are both effected in such manner that inaccurate operation as the result of torsional elasticity of the gear supporting shaft is prevented. While the moving parts have sufficient rigidity and strength for the intended purpose, the mass of those parts which execute reciprocating movement may be reduced to a minimum with consequent reduction in vibration.

An automatic pressure applying mechanism is illustrated in Figure 4 and includes a shaft |30 to which the rack 18 may be directly secured, the shaft |30 extending within a casing |3| carried by the head portion 3| of the frame.

in which is slidably supported a cylinder 32 having an integral head |33 at one end thereof and a removable head |34 at the other end, suitable packing means indicated at |35 to permit the passage of the shaft |30 therethrough and to seal the interior of the cylinder being provided. Fluid pressure conduits |36 and 31 communicate .with the interior of the cylinder at either end through ports in the cylinder heads |34 and |33 respectively. The cylinder 32 is normally retained against axial displacement in the housing I3! by a plurality of friction elements |40, each such element being supported in an aperture in thev housing and being pressed into engagement with the adjacent wall of the cylinder |32 by means of a coil spring |42, the degree of compression of the latter being adjustable by means-of the threaded abutment |43.

Fitting within the cylinder is a piston |45 which is slidable therein in a conventional manner, the piston being hollow and having end walls |41 and |48, the latter being detachable.r The shaft 30 extends through the piston and sleeves |50 and |5I, slidably mounted on the shaft |30, are disposed within the piston |45, these sleeves having abutments on their outer ends in the form of nuts |53 and |52 which are threaded on the respective sleeves and which may engage the outer faces of the end walls |41 and |48 of the piston.

Located within the pistonY I 45 and secured to the shaft v|30 substantially centrally of the piston is an abutment |54. The sleeves |50 and are retained in engagement with this abutment by means of coil springs |56 and |51, these springs engaging at their opposite ends `the respective end walls |41 and |48 of the piston.

Thel casing |3| is provided with a cylindrical bore Each sleeve is constructed to provide a shoulder which, inthe position which the parts occupy in Figure 4 of the drawings, is spaced from the adjacent end wall of the casing to a slight eX- tent. Thus a clearance space |59 is afforded between the sleeve and the end Wall |41 of the piston and a clearance space |60 is afforded between the sleeve |5I and the end wall |48 of the piston to permit axial movement of the sleeves with respect to the piston.

Means are provided for alternately supplying fluid, for instance air, under pressure to the opposite ends of the cylinder |32 through the conduits |36 and 31. Thus each of these conduits is connected through a flexible hose or the like to a valve casing |62 within which is disposed a rotatable valve element |63. The valve element |63 is provided at its periphery with passages |65 and |66 each extending partly around the element. The passage |66 communicates through a passage |63 with the outer surface of the valve element and thus constitutes a vent to atmosphere. The passage communicates through a passage |69 with a conduit |10 through which air under pressure is supplied. The conduit |36 is in communication with a port |12 extending through the valve casing and arranged to communicate with the passages |65 and |66 successively as the valve element |63 is rotated, and conduit |31 similarly communicates with the passages |65 and |66 successively through a port |13. The valve element |63 may be secured in position within the casing by means of a nut |15 threaded on one end thereof and may be rotated by means of a worm gear |16 which may be formed integrally therewith. Engaging the worm gear is a worm |18 secured to or formed on a shaft |19 which is suitably supported on the frame, the shaft |19 having secured thereto a pulley which may be driven by means of a belt |32 from a pulley |83 secured on the shaft 60 hereinbefore described.

The operation of the structure shown in Figure 4 will be apparent from an inspection of diagrammatic Figures 1'1 to 23 inclusive which illustrate the successive positions assumed by the component parts of the structure. Thus in Figure 17 the parts are shown in the position which they occupy immediately prior to the reversal of the dircction of torque applied to the gear 31 for the purpose of lapping the opposite faces of the teeth thereof. It will be seen that the piston |45 occupies a position to the extreme left, the cylinder 32 is at the extreme right of its movement with the end wall V|34 thereof in engagement with the left end of the piston, and the abutment |54 occupies an intermediateposition with respect to the end walls |41 and |48 of the piston, neither of the springs |56 or |51 being capable of eX- pansion to displace the abutment |54. Air or other fluid under pressure is now admitted to the left-hand end of the cylinder |32 through the conduit |36, the right-hand end of the cyls inder being vented to the atmosphere. This result is achieved by the rotation of the valve element |63 to a position in which the passage |65 to which compressed airis supplied is just entering into communica-tion with the conduit |36 While the passage |66 which is vented is just entering into communication with the conduit |31. Communication of the passages 65 and |66 with the conduits |36 and |31 respectively will now be maintained until the valve element |63 has rotated through nearly 180.

The piston Iiii will now be displaced to the right, compressing the spring |51 and shifting the rack 18 to eiect rotative displacement of the gear 31 to the extent necessary to contact the opposite working faces of the gear teeth with the opposed faces of the lap 63. Further displacement of the piston |45 to the right is preve-nted since the gear 31 which is directly connected to the abutment |54 can partake of no further displacement. While this clearance between the teeth of the gear and lap is being taken up by movement of the piston |45, the cylinder |32 is retained against movement by the friction elements Idil, the elimination of clearance between the cooperating teeth and the compression of the spring |51 requiring little effort as compared with the force required to displace the cylinder |32 against the action of the friction elements Me. The parts now occupy the position in which they are shown in Figure 18 of the drawings.

It is not desired that the pressure of the air introduced in the cylinder |32 will be exerted between the teeth oi the gear and lap since variation in the pressure of the air supplied would result in lack of uniformity in the grinding operation and the delicate pressure which is important in an operation of this character is diihcult to secure by the use of compressed air, it being intended that reliance shall be placed solely on the spring |51 for exerting the necessary pressure between the cooperating teeth. Thus when the parts have assumed the position shown in Fig. 18, the cylinder |32 is displaced to the left by the action of the compressed air between the end wall |48 of the piston and the I4 cylinder head |35, the air pressure building up to vthe extent necessary to overcome the resistance of the friction elements |43. Displacement of the cylinder |32 to the left is limited by en'- gagement of the cylinder head |33 with the end wall |41 of the piston, the position of the parts being shown in Figure 19. It will now be observed that the spring |51 is still under compression, and this spring will gradually expand as material is removed by the abrasive action A between the teeth and the gear and lap, expansion of the spring being limited by engagement of the nuts |52 on the sleeve |5| with the end wall |48 of the piston when the parts occupy the position in which they are shown in Figure 20.

When e-xpansion of the spring |51 is completed, no further pressure will be applied between the teeth of the gear and lap and the amount of material removed therefrom may thus be accurately determined in advance by establishment of the clearance |60 between the sleeve |5| and the end wall |48 of the piston, Nhile adjustment of this clearance is ordinarily not necessary, it is obvious that the clearance may be readily altered if desired by the use of shims intermediate the abutment |54 and the sleeve |5I, suitable adjustment of the nuts |52 being effected.

Ordinarily the grinding operation o n the enseries of operations will now taire place, the gear 31 being rst displaced to take up clearance between the teeth of the gear and lap and backlash in the connections between the gear and the abutment |54. and the spring |55 will be compressed to apply the pressure necessary for proper abrasive action between the cooperating teeth. The successive positions of the parts during these reversed operations are shown in Figures 21 to 23 inclusive and need not be described, the fourth and last position being of course that corresponding to Figure 17. At this point, since grinding has been completed to the required extent, the operation of the machine may be interrupted, some suitable indicating device being employed, if desired, to warn the operator that the end of the cycle has been reached, or the mechanism may be adjusted to permit the grinding of each of the working faces of the gear teeth several times before the desired amount of material is removed. In lieu of the employment of an indicating device, the supply of pressure fluid may be interrupted, for example by the provision of a slip or friction coupling in the gearing which rotates the valve element I3 and cooperating abutments on the frame and on the gear |16 or valve element, one of these Vabutments Vbeing manually movable so that operation may be resumed when desired. Ordinarily, however, several cycles of operation are completed before the gear is finally finished, the gear being periodically indexed with respect to the lap in order to obtain greater uniformity of contour of the working faces of the gear teeth as hereinbefore described. While the grinding may be continued to any desired extent, theoperator is enabledvwithout relying on his sense of touch to determine at any stage precisely to what extent the grinding is completed.

In order that production may be speeded up and the cost of construction and expense of operation reduced to a minimum, it is desirable to provide a battery of these machines such as shown in Figure 24 in which a number of gears may be simultaneously lapped, the mechanism for controlling the lapping of each gear being driven from a common motor 65 and the supply of compressed air being regulated by valve mechanism within a single valve casing |52. In view of the general similarity of construction shown in Figure 24 with that hereinbefore described,

similar reference numerals are employed. 'Ihus reciprocation of each of the gears being lapped is eiected through a common drive shaft |85, bevel gears |36 being provided to drive the several operating shafts 6i! of the` lapping units from this shaft. The shaft |35 is operable by belt gearing from the motor 65, the shaft |19 which drives the worm gear |16 controlling the valve mechanism being operable through belt gearing from the shaft |35.

While a single valve casing |32 may be placed in communication with the cylinders within the several iiuid pressure casings |3| by suitable conduits, not shown in the drawings, it may be found desirable in order to avoid the delayed action resulting from the time required to build up pressure through a relatively long conduit and to vent to atmosphere therethrough, to supply separate valve casings |52 for each of the units of the series, the valve elements within these casings being driven from a common shaft |19 which is supported in the frame and extends transversely of and at the rear of the units.

It Will be apparent from vthe foregoing description that certain features of the invention are equally applicable to machines in which the circumferential tooth pressure is applied man.- ually as to machines. in which this pressure is automatically controlled. It will further be ap- 1. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means for applying torque to said members to establish circumferential pressure between the toothed portions thereof, of means operatively associated with said irst named means for interrupting the applicationof such torque thereby on completion of a predetedmined relative rotative displacement of said members resulting from the removal of material from the toothed portions thereof, and means operable in timed relation with said mechanism and associated with said first named means for reversing the direction of applied torque.

2. In apparatus for lapping gears` of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means for applying torque to said members to establish circumferential pressure between the toothed portions thereof, of means associated with said rst named means and operable in timed relation with said mechanism for periodically reversing the direction of applied torque.

3. The combination claimed in claim 2 in which a common source of motive power is provided to drive said mechanism and said last named means.

4. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means for effecting relative rotation of said members to the extent required to engage one working face of the teeth of the gear member with the opposed working face of the teeth of the lap member and for applying pressure between the said engaged tooth faces, lsaid means including an element displaceable to the extent required to engage the cooperating tooth faces of the lap and gear members, Aand a second element displaceable with said first element in engaging the said tooth faces, said second element being further displaceable with respect to said first element to an extent sufficient to maintain the pressure between the engaged faces during removal of material therefrom, and means driven in timed relation with said mechanism for periodically reversing the direction of displacement of said elements to lap opposite faces of the teeth of the gear member.

5. In apparatus for 'lapping gears of the type Having thus described the invention, what is comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means for effecting relative rotation of said members to the extent required to engage one working face of the teeth of the gear member with the opposed working face of the teeth of the lap member and for applying pressure between the said engaged tooth faces, said means including an element displaceable to the extent .required to engage the cooperating tooth faces of the lap and gear members, and a second element displaceable with said iirst element in engaging the said tooth faces, said second element being further displaceable with respect to said rst element to an extent sufficient to maintain the pressure between the engaged faces during removal of material therefrom, means for limiting the extent of displacement of said second element, whereby the amount of material removed from the opposed tooth faces of said members may be predetermined, and means driven in timed relation with said mechanism for periodically reversing the direction of displacement of said elements to lap opposite faces of the teeth of the gear member.

6. In a mechanical movement, the combination with a member supported for reciprocal movement, of means for applying force to said member tending to reciprocate the same, said means including a piston having a resilient connection with said member, a cylinder in which said piston is disposed to afford a working chamber at either side of the piston, said cylinder being sup-ported for axial displacement limited in either direction by Ysaid piston, means yieldably restraining said cylinderv against axial displacement, and means for alternately admitting uid under pressure to opposite sides of said piston, whereby on the admission of pressure fiuid to said cylinder at either side of said piston, said resilient connection will be stressed and said cylinder displaced to the extent of movement thereof to render the fluid pressure ineffective.

7. In a mechanical movement, the combination with a member supported for reciprocal movement, of means for applying force to said member tending to reciprocate the same, said means including a piston having a resilient connection with said member, a cylinder in which said piston is disposed to afford a working chamber at either side of the piston, said cylinder being supported for axial displacement limited in either direction by said piston, means yieldably restraining said cylinder against axial displacement, said last named means being sufficiently effective to restrain the cylinder against the action of said resilient connection when the latter is stressed, and means for alternately admitting fluid under pressure to opposite sides of said piston, whereby on the admission of pressure uid to said cylinder at either side of said piston, said resilient connection will be stressed and said cylinder displaced to the extent of movement thereof to render the fluid pressure ineffective.

8. In apparatus for lapping the teeth of external helically toothed gears, the combination with a lap support, of an internally toothed' lap carried in fixed position by said support, a frame having a portion extending above said support, a shaft supported on said frame for substantially vertical reciprocatory movement and for rotation about a substantially vertical axis, said shaft lappedin meshing relation with said lap, means a sociated with said frame for imparting rotato said shaft during reciprocatory movement ci, said means including a sleeve having a oai toothed connection with said shait, means for maintaining said sleeve against displacement axially of the sha-it, and means for rotating said sleeve, whereby circumferential pressure may be applied to the cooperating teeth of the gear and lap.

9. In a machine for lapping helically toothed gears, combination with a lap and a lap support, of means for securing said lap in fixed position on said. support, a gear supporting shaft hav' ig the axis thereof coinciding with the axis of the lap and cari' ing a gear in meshing relation with said a carrier for said shaft supported .for rec coating movement, a crank and pitinan drive .for said carrier, and means for imparting rotation to said shaft, said means including normally fixed member, a helical cam connec -on between said carrier and said xed member, a rotative coupling between said carrier and said crank and pitman drive therefor, and means for displacing said iixed member to apply torque to said carrier and shaft, whereby pressiue may be applied. to the cooperating working faces oi the gear and lap.

l0. In a gear lapping machine, the combination with a toothed lap member, of a support for said member, a support for a toothed gear member to be lapped, said supports carrying said members in intermeshin Jr relation, means for reciprocating at least one of said supports and the member carried thereby, and guide means associated with a reciproca-ted support for constraining the latter to follow the generally axial direction oi the teeth of the gear and lap members during such reciprocation, said means for reciprocating said support being disposed above said guide means and being operatively connected with said support adjacent the upper end oi the latter.

ll. In apparatus for lapping the teeth of external helically toothed gears, the combination with a lap support, of an internally toothed lap carried in hired position by said support, a frame having a portion extending above said support, a shaft supported on said frame for substantially vertical reciprccatory movement and for rotation about a substantially vertical axis, said shaft having a portion adapted to support a gear to be lapped in meshing relation with said lap guide means associated with said frame for imparting rotation to said shaft during reciprocatory movement there-oi', said means being operatively connected with said shaft above and in proximity to said lap, means carried by said frame and operatively connected with the upper endof said shaft for reciprocating the latter, said last named means comprising a crank and pitman device having a non-adjustable throw.

l2. In a gear lapping machine, the combination with a toothedy lap member, of a support for said member, a support for a toothed gear member to be lapped, said supports carrying said members in intermeshing relation, means for reciprocating at least one of said supports and the member carried thereby, a basin disposed beneath said members and adapted to receive a mechanical suspension of abrasive material in liquid to a level suillcient to ensure the wetting of the reciprocated member in the lower position of the latter, and means for agitating the liquid to prevent the abrasive from settling.

13. In a gear lapping machine, the combination with a toothed lap member, of a support for said member, a support for a toothed gear member to be lapped, said supports carrying said members in intermeshing relation, means for reciprocating at least one of said supports and the member carried thereby, a basin disposed beneath said members and adapted to receive amechanical suspension of abrasive material in liquid to a level suflicient to ensure the wetting of the reciprocated member in the lower position of the latter, and means for introducing air under pressure into said liquid.

la. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed tooth portions, a support for a lap member, a catch basin disposed therebeneath, and means for moving said catch basin vertically.

l5. In apparatus for lapping gears of the type comprising mechanism for imparting relative' motion to a lap member and a gear member havingintermeshed tooth portions, a frame member, a lap support carried by said frame member, a catch basin carried by said frame member and disposed beneath lsaid lap support, and means associated with said frame member for moving said catch basin vertically.

16. In apparatus for lapping gears of the type Comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means for applying torque to said members to establish circumferential pressure between the toothed portions thereof, and automatic means'for determining, in advance of a series vof operations on a succession of gear members, the maximum amount of material to be removed from any one tooth of any of such gear members'said means including devices operatively associated with said rst named means for interrupting the application of such torque thereby on completion of a predetermined relative rotative displacement of said members resulting ,from the removal of material from the toothed portions.

17. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means for applying substantially constant and predetermined torque to said members to establish circumferential pressure between the toothed portions thereof, and automatic mea-ns for determining, in advance of a series of operations on a succession of gear members, the maximum amount of material to be removed from any one tooth of any of such gear memberasaid means including devices operatively associated with said i'lrst named means for interrupting the application of such torque thereby on completion of a predetermined relative rotative displacement of said members resulting from the removal of material from the toothed portions.

18. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with automatic means for effecting relative rotation of said members to the extent required to engage one working face of the teeth of the gear member with the opposed working face of the teeth of the lap member and for applying pressure between the said engaged tooth faces, of means operatively associated with said rst namedmeans for interrupting such application ofipressure thereby on completion of a predetermined relative rotative displacement of said members resulting from the removal of material from the toothed portions thereof.'

19. In apparatus 'for lapping gears of the type comprising mechanismv for imparting relative motion toa lap member and a gear Lmember having intermeshed toothed portions, the combination with'automatic means for effecting-rela'- tive rotation of said members to the ex-tent required-to engage one working face of the teeth of the gear fmernber with the opposed working facewof the teeth of the lap member and for applying pressure between the said engaged tooth faces, of means operatively associated with said first named means for interrupting such application of pressure thereby on completion of a predetermined relative rotative displacement of said members resulting from the removal of material from the toothed portions thereof, said second named means acting independently of the initial tooth clearance in interrupting the application of pressure by said first named means.

20. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means for effecting relative rotation of said members to the extent required to engage one working face of the teeth of the gear member with the opposed working face of the teeth of the lap member and for applying pressure between the said engaged tooth faces, said means including an element displaceable through a distance determined by the extent of relative displacement required to engage the cooperating tooth faces of the lap and gear members, a second element displaceable with said rst element in engaging the said tooth faces, and means fo-r further displacing said second element with respect to said first element to an extent suilicient toy maintain the pressure between the engaged faces during removal of material therefrom, and means f-or limiting the extent of displacement of said second element, whereby the amount of material removed from the opposed tooth faces of said members may be predetermined.

21. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with an energy storing device operatively connected with at least one of said members to apply continuous circumferential pressure between the toothed portions of said members, of means including a Huid pressure device acting independently for effecting relative rotative movement of said members to engage opposed working faces of the teeth thereof, said fluid pressure device being operatively connected to said energy storing device to supply energy to the latter.

22. In :apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with an energy storing device operatively connected with at least one of said members to apply circumferential pressure between the toothed portions of said members, of a uid pressure device for effecting relative rotative movement of said members to engage opposed working faces of the teeth thereof, said fluid pressure device beingr operatively connected to "said energy storing device to supply energy to thel latter, and means whereby said fluid ressure `device-is rendered inoperative while said energy storing vdevice is operating 'to'supply pressure between said members.

23. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with an energy .storing device operatively connected-with at least one of said members to applycircumferential pressure between the -toothed portions of said members, of means separate from said mechanism and including a fluid with means for applying torque to said members to establish continuous circumferential pressure between the toothed portions thereof, of means separate from said mechanism and including a fluid pressure actuated device for initiating operation of said first-named means.

25. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means including a spring for applying torque to said members to establish continuous circumferential pressure between the tootlhed portions thereof, of'means separate from said mechanism and including a fluid pressure actuated device for loading said spring.

26. In apparatus for lapping gears of the type comprising mechanism for imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combination with means including a spring for applying torque tosaid members to establish continuous circumferential pressure between the toothed portions thereof, of means separate from said mechanism and including a fluid pressure actuated device for compressing said spring to a predetermined extent only.

27. In apparatus for lapping gears of the type comprising mechanism, forl imparting relative motion to a lap member and a gear member having intermeshed toothed portions, the combina.- tion with means including a spring for -applying torque to said members to establish continuous circumferential pressure between the toothed portions thereof, of means separate from said mechanism and including a fluid pressure actuated device for compressing said spring to a predetermined extent only, and means for limiting the expansion of said spring.

28. In apparatus for lapping the teeth of externally toothed gears, the combination` with a lap support, of an internally toothed lap carried in fixed position by said support, a frame having a portion extending above said support, a shaft supported on said frame for substantially vertical reciprocatory movement and for rotation about a substantially vertical axis, said shaft having a portion adapted to support a'gear to be lapped in meshing relation with said lap, means associated with said frame for guiding said shaft to cause the gear to follow the lap teeth during reciprocatory movement of said shaft, and means for rotating said shaft to provide circumferential pressure between the teeth of the gear and lap, said last named means being disposed sufficiently close to the gear to avoid undesirable torsional springing of said shaft.

29. In apparatus for lapping the teeth of external helically toothed gears, the combination with a lap support, of an internally toothed lap carried in fixed position by said support, a frame having a portion extending above said support,

a shaft supported on said frame for'substan- 15 .tially vertical reciprocatory movement and for rotation about a substantially vertical axis, said shaft having a portion adapted to support a gear to be lapped in meshing relation with said lap, means associated with said frame for imparting rotation to said shaft during reciprocatory movement to cause the gear teeth to follow the lap teeth, and meansl associated with and' acting through said rst means for rotating said 10 shaft to provide circumferential pressure between the teeth of the gear and lap, said last named means being disposed suiiiciently close to the gear to avoid undesirable torsional springing of said shaft. f

JOHN M. CHRISTMAN. 

